Nudibranchs are shell-less marine mollusc which appear to employ a chemical defense mechanism against predators. They generally sequestered the defensive products from marine sponges on which the nudibranchs feed, and store them in their bodies. In this time, the study of the defensive chemicals of Japanese Chromodorididae nudibranch Chromodoris inornata, collected along the coast of Fukuoka is conducted, and from the CHCl_3 soluble part of the whole bodies of the nudibranch, ten sesterterpenoids (1)-(10) were isolated. Their structures have been elucidated by means of the spectroscopic data and single crystal X-ray analyses. Terpenoids (1)-(6) were classified as scalarin derivative. Terpenoid 7 were grouped into furoscalarol (or scalarolbutenolide)-type sesterterpenoid. Terpenoid 8 bears cheilanthane skeleton(16, 24-oxidocheilanthane). Terpenoids 9 and 10 have a novel carbon skeleton based on different arrangements of side chain of cheilanthane. Terpenoids 7, 8, and 10 revealed cytotoxic activities against murine lymphoma L1210 and human epidermoid carcinoma KB cell lines. To the author's knowledge, 2, 4, 5, 6, 7, 8, 9, and 10 are new sesterterpenoids.